Automatic telephony.



C. L. GOODRUM.

AUTOMATIC TELEPHONY. APPLICATION FILED JUNE 18, 1912.

Patented July 27, 1915.

3 SHEETS-SHEET l.

COLUMBIA PLANDGRAPH C0, WASHINGTON, D. c.

C. L.-GOODRUM.

AUTOMATIC TELEPHONY.

APPLICATION FILED JUNE 18. 1912.

Patented July 27, 1915.

3 SHEETS-SHEET 2.

Int e110!" 1 a imme/om C. L. GOODRUM.

AUTOMATIC TELEPHONY.

APPLICATION FILED JUNE 16, 1912.

Patehted July 27, 1915.

3 SHEETS-SHEET 3.

I I l I I I I I I I I a I I I I l I I 1 l I COLUMBIA PLANMDAPH ccnwAsnmh'mrl. D.c.

CHARLES GOODRUM, 0F ATHENS, GEORGIA, AssieNon, BY MEsNE assremvrnurs, 1'0 WESTERN- ELECTRIGOOMPANY, or NEW YORK, N. Y., A oonPonA'rIoNor-rumors.

AUTOMATIC TELEPHONY.

Specification of Letters Patent. 1 Patented July 27, 1915.

Application filed June 18, 1912. Serial N 0. 704,274.

To all whom it may concern Be it known that I, CHARLES L. GooDRUM,

a citizen of the United States, residing at Athens, in the county of Clark and State of Georgia, have invented-certain new and useful Improvements in Automatic Teleph-- ony, of which the following is a specification.

My invention relates to improvements in automatic telephony and particularly to the arrangement of automatic switches and the circuits for the same to efi'ect interconnection between subscribers at an exchange without the use of operators.

One of the objects of my invention is to provide means for reducing the number of contacts and simplify the switches commonly known as the selector switches and in carrying out this invention I employ the flat or one-movement switches of the Lattig and Goodrum type in which contacts arranged in permanent banks are adapted to be successively engaged by wipers rotated across them, as distinguished from those systems having two-movement, or what is known as up-and-around, switches for first picking out a group and then a contact in the group, such as the so-called Strowger system.

One of the principal features of my invention is the employment ofintermediate testing or finder switches which are automatically operated to find a subsoribers line or a trunk which has been connected by a selector switch operated by the usual calling device at the subscribers station to a calling line.

In the early history of the so-called Lattig and Goodrum system, finder switches were employed to find the subscribers line and automatically connect them to a first selector, thus dispensing with the individual first selector of the automatic system then in use, the subsequent finding of groups and idle trunks in these groups leading to other switches being accomplished in the then well known way. In such cases these selectors would select a group, by impulses from the o'perators calling device and then automatically find an idle trunk in this group. In the present system I'employthe same finder system for finding the line and con necting it to an idle selector from the banks of which trunks lead to different groups of other selector or connector switches depending ,on the size of the exchange. Intermediate finders are. then employed at each J group for finding the trunk and the selector switch which has been connected to the line; these finders are tied'to the next selector or connector switch as the .case "be, and, if a selector switch, it isagain operated to find a trunk leading to another group which would be again picked out or found; by .another intermediate finder or back testing switch for the group selected and so on through a third selector or connector, the last intermediate finder being tied to the connector switch in the group desired which is then operated in the usual, way to select the called line.v p

In the accompanying drawings: Figure l/is a diagrammatic view showing 'a subscribers station and a finder switch for selecting the calling line and connecting it to the first selector switch, there being also shown in this figure a distributing switch for distributing calls to the different; finder switches, this distributing switch being the subject matter of other applicationsand not a part of this, invention. Fig. 2 is ,a. diagrammatic view of the first,selectorswitch and the intermediate finder or back-test switch for finding the trunk selected by the-selector switch; this first selectorswitch being tied to the line finding switch of Fig. 1. Fig. 3 is a diagrammatic view of the intermediate or back test finder for finding the trunk selected by the second selector and also'the connections to the called line.

It may be noted that the drawings'by besheet adjacent to thebottom of the next and so on will show the connections extending through and between the various switches.

Like parts are represented by similar characters of references in the several views.

Referring now to Fig. 1, the subscribers station A is equipped with the usual apparatus for common battery installation consisting of a transmitter, 1, receiver ,2, book switch 3, ringert, condenser-5, and a sending device 6, for transmitting impulses for operating the switches at the exchange. Theline and mate conductorsa and a from each subscribers station terminate in contacts a and o in the bankofthe line finding switch F; these line and mate conductors being multiplied to other finderswitches in the usual way. The line and mate conducrelay a through the circuit breakers a and a of the cut-ofi' relay B, the circuit for this relay a being from the conductor a, by Wire 7, spring a contact 8, wire 9, relay (4*, wire 10, battery 11, conductor 12, contact 13, spring 66 wire 14, to conductor a so that closing the subscribers line at the hookswitch 3 operates the line relay a Belay a when magnetized operates grounded spring a and causes it to move away from the contact 15 and engage contact 16. Contact 15 is connected by line 17 to a bank contact 18 in the finder switch, while contact 16 is connected by wire 19 through the distributing switch cl and wire 19 to the starting circuit of line finder switch F. For the purpose of this invention the distributer switch may be omitted and the wire 19 may be considered as connected directly to the wire 19 as the distributer switch simply distributes calls to different finder switches of which F is one, the result being that when the line relay 00* is operated the switch F is started to find the operated line as follows: The wire 19 connects with ofi-11ormal spring 0 of the finder switch F which normally engages contact 20 connected by wire 21, contact 22 and spring 23 to the motor magnet (Z to battery and ground. The motor magnet d operates the switch and causes its wipers to traverse the bank contacts. The initial energizing of the motor magnet d through the off-normal spring 0 causes the switch to make one step when the circuit is opened at contact 22 by the attraction of the spring 23 on the motor magnet (Z, the operating mechanism of the switch being such that it makes one step each time the motor magnet is energized and deenergized in a well known way. As soon as the finder switch takes one step the offnormal spring 0 moves from contact 20 into engagement with contact 24 so that the starting circuit through wire 19 is opened and the impulses necessary to continue the operation of the finder switch must come from another source. The first current impulse which passes over the starter wire and through wire 21 also passes over the branch wire 25 to a controlling relay 6 and thence by wire 26 to battery and ground. This energizes the controlling relay e and operates springs c and e and 0 The spring 6 is thus brought into engagement with contact 27 connected to the line 25 and line 25 is thus connected through spring 6 to line 28 which leads to the wiper 29 of the finder switch F. This wiper 29 is adapted to engage the contacts in the lower row or bank in which is located the contact 18 connected by wire 17 to the contact 15 opened by the energizing of the line wire a The contacts in this row or bank are therefore normally grounded at contact 15 through the springs 64 of the various line relays a so that if the wiper 29 on the first switch movement falls on a grounded contact current is supplied to the motor magnet from battery and ground over the following circuit: From grounded battery, motor magnet d, spring 23, contact 22, wire 25, contact 27, spring a wire 28, wiper 29, contact 18, wire 17, contact 15, spring a to ground. As soon as the wiper falls on the contact 18 01 the line which has been operated, there being no ground on this contact, the line branch being open at contact 15, the finder switch F stops with the wipers a and a resting on the contacts a and a of the line and mate wires or and a which constitute the talking circuit. The switch wipers a and a are connected by line wires a and a directly to the corresponding wipers of the first selector switch S. The dropping back of the relay E causes the spring 6 to engage grounded back contact 30. Spring 6 is connected by wire 31 to switch wiper 32 which engages the third row of bank contacts 33 and these contacts are connected by branch circuits 34 to the cut-ofi relays of the respective lines so that when the wiper 32 rests on one of the contacts 33 which are connected by branch lines 34 to the cut-ofi' relays Z) of the respective lines and thence to battery and ground with the relay 6 deenergized, the cut-off relay Z) is operated over the following circuit: Grounded battery, relay Z), wire 34, contact 33, switch wiper 32, wire 31, spring 6 and grounded contact 30. T 118 energizes the relay 6 which thus attracts spring a and a and breaks the circuit for the line relay a at contacts 8 and 13. When the finder switch F has stopped on the line wires of the calling party and these line wires are thus extended to the first selector switch, the first selector switch is placed in condition to be operated by the controlling relay S This is accomplished as follows: The off-normal spring 0 of the finder switch engaging con tact 24 at the first step of said switch, places ground on the said spring through wire 35 to ground. A branch wire 36 leads from the off-normal spring 0 to contact 37 which is a back contact for the spring 6 of controlling relay 6 and this spring 6 is connected by Wire 38, contact 39, spring f of relay 7 and wire 40 to spring 42 (in the selector switch S) normally engaging back contact 43 connected by wire 44 to the controlling relay S of the selector switch S so that as soon as the finder switch F stops and the controlling relay 6 (in the finder switch, Fig. 1) is deenergized the controlling relay S (Fig. 2) is operated over the circuit just described from grounded ottnormal spring 0 to the said relay and then by wires 45 and 46, battery and ground. The energizing of the relay S closes the armature springs 47 and 48 to contacts 49 and 50 which are tapped onto the extensions a and (4 of the line and mate wires a and (6 these lines a and (a "being connected to the switch wipers a and a of the selector switch. The springs 47 and 48 being thus connected to the line and mate wires-extended, bring these line and mate wires into the operating circuits of the switch so that the switch can be operatedby the impulse sender at the subscribers station and stepped around to the desired group of contacts. As soon as the switch stops uponthe group terminals asecond or intermediate finder or back test switch F is started which finds the trunks leading from the terminals selected. This is accomplished as follows: The starter wire 51 of the finder switch F is connected through the distributer switch D as before described, to wire 51 which leads to'the terininalcontact 52 on the bottom-row of terminals inthe selector switch bank, which is I adapted to be engaged by wiper 53 as the switch advances and which wiper will, in the operation of the switch, be grounded so that a starting impulse is given-to the intermediate finder or test switch F to cause it to start and find the trunks a and a selected by the selector switch. The main wipers a and a of this intermediate finder or back test switch are connected by wires a and a to the main selecting wipers of the connector switch C shown in Fig. 3,'so that after the intermediate finder orvback test switch F has found the trunk selected by the selector switch S, the connector switch will be connected directly to the calling subscribers station and the connection to the called subscriber will be made by the operation of the impulse sending device in the usual way.

I-have shown only one selector switch and consequently one intermediate finder. If other selectors are necessary owing to the size of the exchange they would be connected up in a similar way. The intermediate or second finder switch F would be connected to the second selector which would be operated from the impulse sending device at the calling subscribers station as in the case of the first selector and the third finder would be employed'to find the group trunks selected by the second selector and ifnecessary this finder switch would be; connected to a third selector and an intermediate finder and thence to the connector, the system being extended as is necessary to accommodate the ultimate size of the exchange The particular form of the selector and connector switches is unimportant as various forms of switches wellknown may be used for making the group selection from impulses from the subscribers Sendingdevice but I will describe briefly the operation of the switches as I have illustrated them. I Taking up the selector switch the operation of the controlling relay S operating its armature springs 47 and 48 energizes the operating relay S over the following circuit: grounded spring 47, contact 49, line wire at, mate a, line switch F, line and mate a and 0%, closed substation, contact 50,

spring 48, wire 54, operating relay S wires 55 and'56 to battery and ground. The relay S when energized attracts springs 57 and 58. Spring 58 is grounded and when attractedfengages contact 59 which is connected by wire'60 to slow relay S thence by I wires 61 and 56 to battery and" ground;.re1ay S is thus energized. Relay-S is also oper? ated when the lines areclosed through from the selector switch'S as follows: Spring 47 of relay S is grounded} and when relay S is energized this groundis from contact 49 tapped onto linewire a which is connected to wiper a Wipers normallyrests on a contact 62 which is connected by wire 63 to relay S"? thence by wire 64 to front contact 65 and armature spring 66 on relay S this armature spring being connected by wire 67 I to wire56 and to battery and ground, so that the closing of relay S followed by the ener gizing of; relays S and S will alsoenergize relay S These four relays S S S and S will allbe energized as the result of the finding of the line by the finder switch and the transfer of the talking circuit to the wipers of the selector switch S. iRelays S and S are slow relays, while relay S is a normal relay and will respond to impulses of'current coming thereto through the contacts 50' and" 49 tapped onto the lineand mate wires a and a Spring 58 of relay S has a back contact 68, and this is connected by wire 69 to 'motor' inagnet S the other end of whose coil is connected by wire 70. to contact 71 of gized a vibration of the spring 58 causedby the energizing and deenergizing of relay S by impulses in the line wires will causethese impulses to be transferred to the motor magnet S over the circuit last described, these vibrations serving also to alternately open andclose in fairly rapid succession the circuitofthe slow relay S 'and cause said relay tohold up as'long as the impulsesare pass- :ing through it, thus keeping the circuit of the motor magnet closed at contactv 65. It.

will thus be seen that the impulses coming f from the subscribers sending device will cause the relay S to be energized "and deenergized which will in turn energize and de'e'nergize the motor .magnet S and cause the switch to be advanced one step 'at each impulse. The first impulse of the switch moves the wiper a ofl? the contact 62 and the circuit for the relay S would thus ,1061 broken at this point, but when relayT'S was &

energized it pulled up an armature spring 7 1 against contact which is connected by wire 76 to back contact on spring 57 of relay S which spring is connected by wire 7 8 to wire 63 leading to the relay S so that as the relay S (which 1 call the operating relay) is operated in response to the impulse sending device, impulses will be given to the relay $53 over the circuit last described and by wire 64, contact 65, spring 66, wires 67 and 56 to battery and ground; this relay being a slow relay will be held up so long as these impulses continue. After the first step of the switch therefore the slow relays S and S and relay S are controlled by the operating relay S The motor magnet being vibrated in unison with the operating relay and the slow relay S getting impulses of current from the for ard contact and the relay S getting impulses of current from a back contact with the circuit-for the motor magnet going through contacts on both of these slow relays, the switch wipers are thus operated in response to the impulses until the wipers reach the desired group of contacts. As soon as the impulses cease, the lines still being closed at the subscribers station with the telephone oil the hook, the relay S will remain energized. This will break the circuit of relay S at contact 57 and relay 8* will become deenergized and will break the. circuit for the motor magnet at front contact 7 5 of the relay S and inasmuch as the circuit for the relay S is through one of its own contacts (after the switch has made one step) this motor magnet circuit can not again be established until the switch wipers have returned to normal. The dropping back and deenergizing of the relay S also closes the starting circuit 51 and 51 for the finder switch F The wiper 53 having stopped on the contact 52, this wiper 58 is connected by wire 79, spring 80, contact 81, wire 82, back contact 83 (on relay 8*), wire 84-, contact 85, spring 86, (on relay S to ground. This gives the intermediate finder F an impulse in the manner substantially as described for finder switch F. This finishes the operation of the selector switch until after the intermediate or back finder has "found the trunk which has been selected by its selector switch. In this connection the wipers a and a extend the main lines and talking circuit as before described. The wiper 53 gives the starting impulse'to the back finder switch F and the other wiper 88 rests on the contact 89 which is connected by wire 90 to the contact 91 on 1 the back finder switch. This wiper 88 of the selector switch is connected by wire 92 to relay S and through relay S wire 93 to relay S and thence by wire 94, contact 95, spring 96, wire 97 to battery and ground. This places grounded battery on the wiper 88. The relay S is, however, normally mea /1c shunted over wire 98, branching from wire 91 to contact 99, normally engaged by spring 100 on relay S which spring is connected to wire 93. The relay S is a low resistance relay, while relay S is a high resistance relay for the purpose hereinafter described. The intermediate finder switch F having been thus started by an impulse over the starter wire will continue its operation until its test wiper falls on test contact 91 at which time the main wipers will rest on terminals of the selected trunk groups a and a.

The operation of the intermediate finder F is somewhat difierent from the first finder and I will now proceed to describe it.

The starter wire 51 is connected to the offnormal spring 0 which is connected by wire 101 to'the motor magnet f, thence by wire 102, contact 103, spring 104 on the motor magnet, wires 105 and 106, spring 107, back contact 108-to battery and ground so that the motor magnet will be operated. Relay f is in multiple with the motor magnet 7 over the branch wires 109 and 110, leading respectively from the wires 101 and 105, so that it is energized and will be energized simultaneously with the motor magnet. The motor magnet, however, when energized breaks its own circuit at contact 10d but relay f will be held energized by a holding circuit formed in part by its own spring 111, which is grounded through wire 112, engaging contact 113 which is connected by wire 111 to wire 109, so that when this relay is energized its spring 111 closes the holding circuit just described by engaging contact 118. The motor magnet being in multiple with the relay 7, its circuit is also closed through this branch line 111, contact 113, spring 111, wire 112 to ground and the motor magnet will continue to vibrate, breaking its own circuit and reestablishing it and thus the switch will continue to step until the motor magnet circuit is broken at contact iv 108 which occurs when the relay f is energized, and this relay f is energized when the wiper 116 drops onto contact 91, which is supplied with potential over the wire 90 as before described. Wiper 116 is connected by wires 117 and 118 to the relay f and to ground hence the relay 7 is energized the moment the wiper engages the terminal 91 and the switch is stopped by the breaking of the motor magnet circuit. This also breaks the circuit of the relay f which drops back. The relay 7 in dropping back allows the spring 111 to engage the back contact 119 which is also connected to wire 117 thus putting ground on the wiper 116 which maintains the high resistance relay S energized and also prevents any other switch from stopping on its contact. The relay f dropping back also breaks its own circuit and cannot be pulled up again until the switch wipers have returned to normal and the off-normal spring c brought to its normal position. The line and mate wires a and a are thus connected through wire a and a to the connector switch. These lines are preferably held open by relay f whose springs 120 and 121 serve as circuit breakers in the lines a and a. This relay is operated by the energizing of relay 7 from grounded contact 122, spring 123, wire 124, to relay 7, battery and-ground and when f is de'energized, f is also denergized. The relay f is preferably a slow relay so that these contacts are held open for a short time after the relay loses its current. especially desirable as this relay is also operated when the switch is released. The relay f also carries a spring 125 in the switching circuit for the connector switch which extends from the off-normal springc to spring'l27, contact 128 to spring 125, thence by wire 129 to the connector switch, and this switching circuit is also closed at spring 125 when relay f is denergized.

I have now described how the interme diate or back test switch F has found the trunk group selected by the selector switch S in response to impulses from the calling subscribers sending device. The next operation is to select the line by similarimpulses from the sending device and this involves the operation of the connector switch, any well known form of which might be used. The operation of the one which I have illustrated is as follows: The line and mate wires (4 and (r terminate in an operating relay 0 preferably tandem wound, the lines being preferably connected to the difierent windings with battery interposed. The

switching wire 129 (from switch F is connected to switching relay 0 and thence by wire 130'to battery and ground. Both op erating and switching relays" are thus energized at the final action of the intermediate finder F The energizing of the operating relay 0 closes the grounded spring 131 against contact 132 which is connected by wire 133to. relay 0 thence to. battery and ground; It thus energizes relay 0 which is a slow relay. This pulls up the armature spring 134, to contact 135 which is connected by wire 136 to relay 0 which is connected by wire 137 to contact 138,'normally engaged by off-normal spring 0 thence to ground so that relayo is thus energized, this also being a slow relay. 0 in pulling up operates the armature spring 139 against contact 140 which is connected by wire 141 to relay 0*, also a slow relay, which in turn is connected by wire 142 to contact 143 on relay 0 This contact has been engaged by grounded spring 144 on relay 0 so that relay 0 is thus ener ized. '0 is themotor ma et and its cir cuit extends from grounded battery on spring 139, contact 140, wire 145 to the mo This is tor magnet 0 thence by wire 146, contact 147, spring 148, wire 149 to wire142, contact 143, grounded spring 144, the circuit being open at contact-147 by theenergizing of the operating relay 0. The switch is now in condition to be stepped around which is done by successivev break-and-make contacts of the sending device atthe calling subscribers station. Ateach break in the circuit, the operating relay 0 is deenergized and the motor magnet circuit is closed at contact 147 by spring148 which energizes the motor magnet 0 and it will beimmediately broken by the energizing of the operating relay 0. This continues as many times as there are impulses transmitted by the sending device and steps the switch around to the terminals of the called subscribers line. It will be remembered that the preliminary energizing of the relay 0 was through wire 137Iand contact 138, off-normal spring (2 to ground; This ground will be removed at the first step of the switch and the relay 0 is held up by a circuit composed of wire 150, (whichis a branch from wire'137), contact 151, spring 152, wire 153, spring 154, contact f 155, to wire 142 and thence to contact 143,}

will be vibrated in unison with the spring 148 which opens and closes the motor magnet and .spring 144 to ground. The spring 154 circuit and this will furnish impulses to the relay, 0 which, being a slow relay, willremain energized when the impulses cease, so that the circuit for the motor magnet will be' thus held closed at contact'140 so long as the impulses continue in fairly rapid succession, but this circuit will be opened so soon as the impulses cease. It willbe remembered that relay 0 controls the circuit for the relay 0 at spring 139 and contact loo 140 so that so soon as the relay 0 becomes denergized relay 0 will lose its current but to the switch; wipers a and a which represent the extension of the line and mate wiresand which will contact with the ..ter

minals of the called subscribers line, the circuit being open at contacts 156 and 157 The third wiperf160 of the switch is connected by wire 161 to spring 162 of relay 0 which, when the relay. is deenergized, engages contact 163 connected by wire 164, spring 165 to ground so that if relay 0 should be deenergized, ground would be placed upon this third wiper 160 and would operate the cut-off relay 6 of the called subscriber, The spring 162,. however, will v be momentarily held up after the switch has found the line, due to the fact that the relay 0 is a slow relay and is being held up by relay 0 which is also slow to release. Spring 162 therefore will remain momentarily engaged with contact. 166 which is connected by wire 167 through spring 139 on relay 0 wire 168, to relay 0 battery and ground, so that in the event that the called party were busy the switch wiper 160 would find ground over the circuits heretofore described and thus relay 0 would be operated. As soon as relay 0 is energized it locks itself up through wire 169, contact 170, spring 171, contact 143, spring 144 to ground. Inasmuch as this circuit is closed at contact 143 by relay 0 and relay 0 is energized by the energization of the operating relay 0, the relay 0 if operated, would be held energized until the callingparty hangs up and deenergizes the operating relay 0. Relay 0 is also provided with armature spring 17 2 which is connected by wire 17 3 to the busy tone T and this spring 17 2 is, when the relay is energized, in engagement with the contact 173 connected by wire 174 to one side of the line a so that the busy tone is thus transmitted back in the usual way to the calling subscriber and notifies him that the line called is busy. Relay 0 is the ringing relay and in case the called line is not busy and relay '0 is not therefore energized ringing relay 0 will be energized by the drop ping back or deenergizing of relay 0 this being accomplished through the circuit beginning with battery and ground (at relay 0 spring 139, contact 175, wire 176, relay 0?, wire 177, spring 178 on the switching relay 0 contact 179, wire 180, contact 181 (on relay 0 spring 171, contact 143, spring 144 to ground. The energizing of relay 0 closes an interrupted circuit through relay 0 as follows: from grounded battery, interrupter 1, wire 182,, spring 183, contact 184, wire 185, spring 186, (on relay 0), wire 187 to relay 0 and ground. The relay 0 it will be remembered controls the circuit breakers 158 and 159 in the line circuit passing through thewipers a and a and these circuit closers will be periodically opened and closed by the interrupted battery circuit just described and put interrupted ringing current on the line wires through the following circuit: from ground at generator 9, wire 188, spring 189, contact 190, wire 191, back contact 159, thence to wire a and wiper a to the calling subscriber and back over wiper a, wire a, to spring 158, back contact of said spring, wire 192, contact 193 (of relay 0*), spring 194 and to ground thus periodically operating the called subscribers ringer. If the called subscriber should answer by removing his telephone from' the switch hook, and thus. closing the line wire (L26 and a, the relay 0 would be operated by the springs 158 and 159 closing on contact 156 and 157 (from the interrupted battery) thus closing the circuit through those contacts and wires 0. and (Z25 to relay 0 and included battery. The relay 0 being energized energizes relay 0 by operating spring 195 against grounded contact 196, the said spring being connected by wire 197 to relay 0 battery and ground. Relay 0 is thus energized and its armature spring 186 is engaged with contact 198 from battery to ground and thus breaks the interrupted battery circuit for relay 0 (through the springs of relay 0*) heretofore described and energizes said relay 0 through the circuit last described. The relay 0 is thus continuously energized so long as 0 is held up and the talking circuit iscompleted through the condensers 0 and 0 over the line and mate wires extended as heretofore described. It will be understood that the generators and tone devices are of the usual type continuously operated from some suitable source of power. This completes the connection of the calling line to a called line by the aid of the one movement switches and the use of the back test or finding system consisting as heretofore described of first finding the subscribers line and then by an impulse sender connecting it to a group trunk then finding the group trunk and by an impulse sender connecting it to another group trunk or selector and then finding the proper group or line in the selector or connector as the case may be. When the conversation is completed and the subscribers hang up their receivers, the switches will be released in pairs. Thus, the connector and its associated finder switch will be released first and as soon as they start to return to normal a circuit is opened, whichinitiates the first operation in the release of the selector switch and its associated finder. In this system the release of the switches is under the control of either the calling party or the called party and we will assume therefore that the calling party having finished his conversation has hung up his receiver for the purpose of release. In hanging up he opens his line circuit at the hook-switch which breaks the circuit for the operating relay 0 of the connector switch. This in turn breaks the circuit for relay 0 The release magnet of the connector switch is shown at R and its circuit may be traced from ground (at switching relay 0 spring r wire 7, spring and contact 1" (on relay 0 wires 4 and 1' to release magnet R thence by wire r to the intermediate finder switch F (Fig. 2) contact and spring 1' on relay 7 to battery and ground. This energizes the connector release magnet R but this is only the preliminary operation, the switch being released when the magnet is again deenergized. The energizing of release magnet R closes a circuit from grounded spring 144 (at relay 0 through wire, r contact 0*, spring r wire 1", to intermediate finder switch F and the release magnet rf thereof (see Fig. 2). The energizing of the release magnet 17 makes the preliminary step for the release of the intermediate finder switch and also closes a circuit from ground (at relay 7) through wire 1' spring r (on release magnet 77"), contact 7", wire 7 to relay f which energizes said relay f and breaks the circuit at r of release magnet B through wire o and this deenergizes the release magnet R and releases the connector switch. The deenergizing of the release magnet R also opens the circuit at 7' for the release magnet 77 of the intermediate finder switch F and causes it to release. The energizing of the relay 7 also opened the circuit of the line wires (in switch'F so that the wipers are temporarily disconnected in returning to their normal position. Release magnet 1 being deenergized also breaks-the circuit for relay 7 as described and its spring also returns to normal.

It will be remembered that in the selector switch S relays a and s were held up by a circuit through the third wipers 88 and 116 in the respective switches F and S. The circuit extends from ground at relay 7 (in switch F through the two relays s and s to battery and ground at relay 8 (in switch S) passing through back contact 119 on relay f (switch F and back contact 94 on relay 8, (switch 'S). When the switch wipers of F therefore return to normal, this circuit is opened and relays s ands are deenergized and close the release circuit for the selector switch S as follows: from ground at the offnormal spring 0 of the selector switch S through wire r back contact and spring 7 of relay 8, back contact and-spring r of relay .9 back contact and spring 1' of relay 8 wire 1" to release relay R (switch S) thence by wire 9 to back contact and spring 7* on relay f of the line finding switch F to battery and ground. This energizes the release magnet R of the selector switch S as the preliminary step to release the selector switch, and the energizing of the release magnet fr of the line finding switch of Fig. 1 as follows: from grounded spring 58 of relay 3 back contact 68, wire 7*, contact 7", armature spring 1* of release magnet R, Wire 7 to release magnet fr, line finder switch thence by wire 1- back to the selector switch S, back contact 1' and spring 66 of relay 8 wire 67 to bat tery and ground. This energizes the'release magnet 7%" of the line finder switch F allowing it to make a preliminary step for releasing this switch. In pulling up, the release magnet, fr closes the circuit for the relay f in the line finding switch F from grounded spring 1', contact r wire 9, relay f f, to

battery and ground. The energizing of relay f on the closing "of this circuit opens the'circuit for release magnet R of the selector switch at spring andback contact 7" of this relay. This causes the release of the selector switch S and also the deenergizing ofthis release magnet E opens the circuit for the release magnet fr of the finder switch F at contact 7 in the selector switch S (Fig. 2). This deenergizes the release magnet fr which in turn opens the circuit for the relay 7 which in dropping back restores everything to normal. If the called party should hang up first he may also release the switches as follows: Abranch circuit for the release =magnet'R of the connector switch extendsfrom wire W, by wire 1*, to spring and contact 7 on relay 0 wire 1", spring and front contact r on relay 0", wirer to spring and back contact 7' on relay 0 to 1ground. (hen the called party hangs up rst, relay 0?", beingin the line circuit will be released and spring 1" will drop back and close "the releasecircuit just described through the release magnet R back to the other switches as before described and, at the same time the circuit for relay 0" will be opened at contact 196 and 0being a slow relay will hold up momentarily and I then its spring T will drop back and open the branch release circuit just described at the spring and front contact r. The re- I have heretofore stated that dissidered' in following the operation in put- I ting through a call as this distributer switch is only required where several finders in multiple are used, but a brief description thereof is as follows: The starter wires 19 or 51 are connected to terminal contacts engaged by the wiper d and the starter, wire (19 or 51) is connected to wiper al through wire 0Z contact (Z spring 03 wire 03*. The switch being in itsnormal position, wiper al rests on the terminal contact of the nextidle finder switch and. a starting impulse would pass right through the switch by the circuit just described including wiper (Z to the starter wire 19 or 51 as the case may be. Means are providedfor advanclng the wiper al (as soon as the proper finder.

has been set into operation), to the terminal of' the neXt idle finder. The starter wire (19' or 51) which enters this switch is branched at (Z one branch ileadingto the motor magnet (Z thence by wire (i contact cl", spring d wire (Z back contact (1 spring d, wire 0?, battery and ground so 105.. tributerswitches D and D need not be con I that the impulsewhich passes through the distributor switch to start the idle finder also starts the motor magnet (Z of the distributer. This motor magnet 65 energizes and attracts spring against contact which is connected by wire cl to relay (Z and thence by wire (Z contact (Z spring (Z wire (Z to battery and ground. The first movement of the motor magnet also energizes the relay d which in turn breaks the circuit of the motor magnet at contact d That causes the motor magnet to release and the switch wiper al is advanced to the next contact and this continues to operate until the ground at the line relay or in the switch S, which gave the starting impulse, has been removed by the finder switch finding the line or the trunk to which a line has become connected. In the case of the line finder this would occur at the time the cut-off relay is operated and allows the'line relay to drop back and in the case of the intermediate finder or back test it will occur when the relay 5 is operated to open the ground circuit at contact 81, in the selector switch. When the distributer wiper (Z has passed over all the terminals, the wiper 6Z engages grounded contact (Z this wiper d is connected by wire (Z to release magnet (Z thence by wire at, contact (Z spring (5 wire (Z and battery to ground. This operates the release magnet d which closes the circuit of the release relay at contact as follows: grounded spring (Z contact 01 wire (Z relay (Z wire to battery and ground. This energizes the release relay d which breaks the contact for the release magnet and the energizing and deenergizing of the release magnet 6P causes the switch to be released and return to normal. The relay 05 also holds open the circuit of the wiper (Z and while it is returning to normal position the relay 6, being slow, gives this a time interval for the switch to return to normal.

Having thus described my invention, I claim:

1. An automatic telephone system comp "ising a plurality of selector switches and a connector switch, a finder switch associated with each of said selector switches and said connector switch, releasing devices in said switches, a release circuit extending between said. switches, meansto release the Copies of this patent may be obtained connector switch and its associated finder switch, and means to successively release in pairs each of said selector switches and its associated finder switch when the preceding switch and its associated finder is released.

2. An automatic telephone system, comprising a plurality of: selector switches and a connector switch, a finder switch associated with each of said selector switches and said connector switch, releasing devices in said switches, a release circuit extending between said switches, a bridged line relay associated with said connector switch which controls the release of said connector and its associated finder switch, the release of each finder switch controlling the release of the succeeding switch and its associated finder switch.

3. In an automatic telephone system, a connector switch and a finder switch, a release magnet in said connector switch, a bridged line relay controlling the operation of said release magnet, a release magnet associated with said finder switch controlled by the operation of the release magnet of the connector switch, a relay associated with the finder switch controlled by the release magnet in the finder switch, said relay con trolling the oint deenergization of said release magnets to release said switches.

a. In an automatic telephone system, a selector and .a connector switch. a finder switch associated with each of said switches, a release magnet for each of said switches, a bridged line relay controlling the actuation oi said connector release magnet, said connector release magnet controlling the actuation of the finder release magnet, and a relay associated with said finder switch which is operated by the actuation of the finder release magnet and which controls the simultaneous deenergization of said release magets to release the connector and its associated finder switch and a circuit established by the release of said finder switch to cause the joint release of the selector and its associated finder switch.

In testimony whereof, I have hereunto set my hand this 31st day of May, 1912.

CHARLES L. GOODRUM.

Witnesses CHAS. I. WELOI-I, Es'rnna E. PFEIFER.

for five cents each, by addressing the Commissioner of Patents,

Washington, D. G. 

